JPH0719494B2 - Tracking resistant adhesive tape - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tracking resistant pressure-sensitive adhesive tape which is used by being wound between layers of a transformer winding and other coils.

(Prior art) With the recent trend toward smaller and lighter equipment, the creeping stress acting on the surface of the insulator of the equipment has dramatically increased, and in adhesive tapes that are wound and used as interlayer insulation for transformer windings and the like. Are required to improve their tracking resistance significantly.

Conventionally, for interlayer insulation of transformer windings in home appliances,
Polyester adhesive tape and barrier tape (epoxy impregnation / polyester / glass cloth) are used,
The tracking resistance of these insulating tapes is in the range of 250 to less than 400 v when evaluated by the comparative tracking index (hereinafter referred to as CTI) of the IEC method. However, in recent years, the CTI value has been increased to 400 to improve the tracking resistance.
Required to be v or higher.

(Problems to be solved) By the way, in an adhesive insulating tape wound between layers such as a transformer winding and used, in order to avoid a so-called "bowing phenomenon" of the tape at the time of winding, it is considerably flexible. It is necessary to use strong tape. However, increasing the rigidity of the adhesive insulating tape increases the bending rigidity of the tape,
The bending reaction force of the wound tape itself becomes large, and peeling easily occurs at the end end of winding of the adhesive insulating tape.

Therefore, the winding end end of the adhesive insulating tape exists on the surface of the winding layer and may be exposed to the tracking phenomenon, and if the tape winding end end peels off and rises up. A disconnection due to Joule heat generation of the leakage current path of the conductive liquid (water containing salt, dust or ionic contaminants) passing through the end of the tape winding is likely to occur at the end of the tape winding. Discharge occurs instantly at this disconnection, and this discharge causes carbonization at the initial stage of tracking. Therefore, peeling at the winding end of the adhesive insulating tape is one of the causes of the tracking phenomenon.

Conventionally, in order to suppress the tracking phenomenon, it has been practiced to use an insulating material having excellent tracking resistance, or to mix an insulating material with an inorganic powder.

However, in an electric device insulated by winding an adhesive insulating tape, even if a material having excellent tracking resistance is simply used for the insulating tape, if peeling occurs at the winding end of the adhesive insulating tape, the device is The improvement of the tracking resistance of itself cannot be achieved.

An object of the present invention is to provide an insulating layer with excellent tracking resistance,
An object of the present invention is to provide a tracking resistant pressure-sensitive adhesive tape that can be easily formed by eliminating the so-called "bowing phenomenon" when the tape is wound.

(Means for Solving the Problems) The tracking resistant adhesive tape according to the present invention has a comparative tracking index of 400 v or more by the IEC tracking resistance test (IEC112Ver3A method) and an elastic modulus of 20 to 1200 kg.
The adhesive layer is provided on the back surface of the insulating film having a thickness of / mm ² and a thickness of 5 to 150 μm.

In the IEC tracking resistance test, a constant voltage of commercial frequency is applied to the test piece, 0.1% ammonium chloride aqueous solution is dropped on the test piece at 30 second intervals, and the number of drops until the test piece is broken by tracking is determined. The CTI value corresponds to the breakdown voltage when the number of drops is 50.

In the present invention, the elastic modulus is set to 20 to 1200 kg / mm ² and the tape thickness is set to 5 to 150 μm. Below the lower limit of this range, a so-called “bow phenomenon” generally occurs when the adhesive tape is wound. Therefore, it is difficult to wind the adhesive tape smoothly, and above the upper limit, the bending rigidity of the adhesive tape becomes large, and the bending reaction force of the wound adhesive tape becomes large.
This is because the winding end of the adhesive tape is easily peeled off.

(Description of Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view showing an embodiment of the present invention.

In Fig. 1, 1 has a CTI value of 400 V or more and an elastic modulus of 20 to 1
A plastic film with a thickness of 200 kg / mm ² and a thickness of 5 to 150 μm. Polyolefin resin such as polypropylene and polymethylpentene, fluorocarbon resin such as vinylidene fluoride, polytetrafluoroethylene and ethylene tetrafluoroethylene, butyl rubber, A film such as polymethylmethacrylate can be used. Reference numeral 2 denotes an adhesive layer, which may be a synthetic resin adhesive such as an acrylic adhesive, a rubber adhesive, a silicone adhesive, or a material obtained by adding a flame retardant to these adhesives.

The surface of the plastic film 1 may be coated with an underlayer for an adhesive or subjected to an easy adhesion treatment such as a corona discharge treatment.

FIG. 2 shows another embodiment of the present invention.

In Fig. 2, 1 is a surface layer film with a CTI value of 400v or more 1
A composite film obtained by laminating 1 and a support film 12 with an adhesive 13, and the elastic modulus of this composite film is 20 to
The thickness is 1200 kg / mm ² , and the thickness is 5 to 150 μm. 2 is an adhesive layer.

The surface film 11, the polyolefin resin having a heat resistance of polypropylene or more, vinylidene fluoride, polytetrafluoroethylene, any film of a fluorine-based hydrocarbon resin such as ethylene tetrafluoroethylene, the thickness 0.5 ~ 80μm It is preferable to use those of As the support film 12, any one of polyester, polyethylene naphthalate, polyphenylene sulfide, polyether ether ketone, polyimide, thin paper, or epoxy resin-impregnated polyester non-woven fabric or glass cloth having a thickness of 1.5 to about 150 μm is used. it can. Adhesive 13 is polymethylmethacrylate, EE
Hot melt adhesives such as A and EVA can be used, and the thickness is
It is preferably 0.1 to 50 μm.

The reason for setting the thickness of the surface layer to 0.5 to 80 μm is 0.5 μm
The above is advantageous for guaranteeing the tracking resistance of CTI value of 400v or more, and 80μm or less is for eliminating the calm of the composite film and guaranteeing the tape winding workability. This is because it is advantageous. The reason why the thickness of the supporting tape is 1.5 to about 150 μm is that it is advantageous to ensure that the mechanical strength required for winding the tape is 1.5 μm or more, and that the bending of the tape is about 150 μm or less. This is because it is advantageous to prevent peeling at the end of the tape winding due to rigidity. Adhesive thickness 0.1 to 50μ
The reason for setting m is that 0.1 μm or more is advantageous for guaranteeing the interlayer adhesive strength, and 50 μm or less is advantageous for making the thickness of the entire tape 150 μm or less.

FIG. 3 shows another embodiment of the present invention, in which the adhesive film 2 is provided on the other surface of the composite film 1 in which the insulating coating layer 11 having a CTI value of 400 v or more is formed on one surface of the support film 12. The elastic modulus of 1 is 20 to 1200 kg / mm ² , and the thickness is 5 to 15
It is set to 0 μm. Support film 12 in this example
For this, the same one as the embodiment shown in FIG. 2 can be used. For the insulating coating layer 11, a coating and sintering layer of a fluororesin dispersion can be used. Next, the results of the tracking resistance test of the tracking resistance adhesive tape according to the present invention will be described.

Example 1 A film composed of a vinylidene fluoride resin layer and a polymethylmethacrylate resin layer having a thickness of 50 μm was obtained by double-layer melt extrusion, and an acrylic adhesive was applied on the polymethylmethacrylate resin layer to a thickness of 25 μm to obtain a film having a thickness of 75 μm. A tracking resistant adhesive tape was obtained. The elastic modulus of this example product is 140 kg / mm ² . Also, tensile strength (kg / 10mm width)
Was 3.7, the elongation (%) was 180, the withstand voltage was 1.875 kv / 1 min or more, and the continuous usable temperature was 140 ° C.

Example 2 Polypropylene having a thickness of 10 μm and ethylene-vinyl acetate copolymer (EVA) having a thickness of 5 μm were simultaneously extruded and fused by an extruder arranged in parallel, and a polyester film was fused to the ethylene vinyl acetate copolymer layer. Then thickness
A 45 μm composite film was obtained, and an acrylic adhesive layer mixed with a flame retardant was provided on the polyester film surface for a total thickness of 65 μ
m tracking resistant adhesive tape was obtained. The elastic modulus of the product of this example is 570 kg / mm ² . Also, tensile strength (kg / 10
The width (mm width) was 5.6, the elongation (%) was 80, the withstand voltage was 1.875 kv / 1 min or more, and the continuous usable temperature was 120 ° C.

Example 3 A 25 μm-thick polyester film was laminated with a hot roll on the ethylene vinyl acetate copolymer resin surface of a film formed by two-layer extrusion of a polymethylpentene resin and an ethylene vinyl acetate copolymer resin.
An acrylic adhesive layer was provided on the polyester film surface of the 40 μm thick composite film thus obtained,
A tracking resistant adhesive tape having a total thickness of 50 μm was obtained. The elastic modulus of this example product is 530 kg / mm ² . The tensile strength (kg / 10 mm width) was 5.8, the elongation (%) was 100, the withstand voltage was 1.875 kv / 1 min or more, and the continuous usable temperature was 120 ° C.

Comparative Example An acrylic pressure-sensitive adhesive was applied on a polyester film having a thickness of 50 μm to prepare an adhesive tape having a total thickness of 55 μm.

These example products and comparative example products are wrapped once on a cylindrical insulating rod, and the electrodes are arranged by sandwiching the wrap portion,
When the CTI value was measured according to the IEC method tracking resistance test, all of the example products were 600 v or more. On the other hand, in the comparative example product, the lap portion was peeled off and was only 280v.

(Effect of the invention) In the tracking resistant pressure-sensitive adhesive tape according to the present invention, the elastic modulus and the thickness as described above prevent peeling at the winding end and eliminate the so-called "bow phenomenon". Since it can be wound, the CTI value of the tape itself is 400.
Excellent tracking resistance over v can be guaranteed for electrical equipment by easy tape winding work.

[Brief description of drawings]

FIG. 1, FIG. 2 and FIG. 3 are explanatory views showing an embodiment of the present invention. 1 ... Insulation tape with CTI value of 600v or more, 2 ... Adhesive layer.

Claims (4)

[Claims] 1. A comparative tracking index according to the IEC tracking resistance test is 400v or more, and an elastic modulus is 20 to 1200.
kg / mm ^2, tracking resistance adhesive tape, wherein a thickness is provided an adhesive layer on the back surface of the insulating film is 5 to 150 m. 2. The insulating film is a single film, and the single film is made of a fluorocarbon resin such as polypropylene, polymethylpentene, vinylidene fluoride, polytetrafluoroethylene, ethylenetetrafluoroethylene, butyl rubber, polymethylmethacrylate. The tracking resistant pressure-sensitive adhesive tape according to claim 1, which is made of any one of the above. 3. The insulating film has a comparative tracking index of 40.
The tracking resistant pressure-sensitive adhesive tape according to claim 1, which is a composite of a surface layer of 0 v or more and a support film. 4. The surface layer is made of a film of a polyolefin resin having heat resistance of 0.5 to 80 μm or more and having a heat resistance of polypropylene or more, or a fluorine-containing hydrocarbon resin such as vinylidene fluoride, polytetrafluoroethylene or ethylene tetrafluoroethylene. , Support film thickness 1.5 to almost 1
The tracking resistance according to claim (3), which is made of a film of polyester, polyethylene naphthalate, polyphenylene sulfide, polyether ether ketone, polyimide, thin paper, or epoxy resin-impregnated polyester non-woven fabric or glass cloth of 50 μm. Adhesive tape.